The sheets of plastic material, especially those utilized in the manufacture of laminated glazings, are generally stored after manufacture in the form of rolls and are cut in a first cutting operation at dimensions slightly larger than those of the laminated glazing, just before assembly of the components of the glazing. The final trimming, to the configuration of the glazing, is made generally after assembly of the components.
Several means are known for effecting the first cutting. For example one can utilize the mechanical action of a cutting blade such as a razor blade or a knife. One can also cut certain sheets of plastic material by the action of heat. Thus, it is known to cut polyethylene sheets by contact with a heated resistor. To aid in the cleanness of the cut, it is also known to combine a mechanical action with a thermal action, for example by utilizing a cutting tool with a hot blade. Another method of cutting sheets of plastic material involves utilizing the combined action of a cutting tool with ultrasound which facilitates the penetration of the tool into the sheet.
All of the previously cited methods for cutting have different disadvantages. Some soil the sheet being cut; others rapidly age the cutting tool and/or also promote emission of toxic gases.
Thus a cutting tool with a cold blade can promote shavings and shreddings that can settle on the sheet, while contact with a heated resistor or with a heated blade can cause, for example in the case of a polyurethane sheet, carbon deposits on the heated element. The carbon can be deposited on the sheet during a subsequent cutting. However, when the sheet to be cut is transparent or translucent and is utilized in the manufacture of laminated glazings, the particles, especially the shavings and the carbon present on the surface of the sheet and which cannot be buried in the thickness of the latter after its assembly with the other components of the glazing, can cause optical defects in the form of, for example, distortions and/or lense-like distortions. It is therefore necessary to avoid having particulates present during the preparation of the glazing and, in this case, during the cutting of the sheet.
The carbon, as well as the great resistance of certain plastic materials to cutting, especially thermosetting polyurethanes, rapidly age cutting tools which after only ten cutting operations or so must be replaced or resharpened. Frequent changing of the tools influences not only the output and the cutting cadence, but also involves soiling the cutting area by bringing to it, in this case, dust resulting from human intervention.
In addition, when cutting a sheet of polyurethane, contact of the heated blade with the polyrurethane can generate toxic vapors. These vapors can also condense and settle on the neighboring elements of the sheet, which leads to further risks of soiling the sheet.